Glossary

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natural selection

differential reproduction. Some individuals leave more offspring than others, contributing proportionally more gametes to future generations. If the phenotypic characteristics that contribute to greater reproductive success are transmitted through genes to offspring, those offspring should also have a reproductive advantage (assuming a stable environment). Phenotypic characters associated with more fertile individuals are thus augmented in the next generation, whereas characters associated with fewer progeny diminish in relative frequency. Selection thus does not necessarily reflect size, strength, or health, only the relative ability to produce fertile offspring.

Neanderthal
see Homo neanderthalensis.
Neogene
a period in the Cenozoic era on the geologic time scale that approximately dates from 23 million years ago to 1 million years ago; consists of the Miocene and Pliocene epochs; marked by the collision of the North and South American tectonic plates, allowing for the migration of animals between the two continents.
Neolithic
see Upper Paleolithic.
New World monkey
primates that are in the suborder Platyrrhini whose natural habitats are located in Central and South America.
niche
the environment that an organism lives in.
nocturnal
refers to an organism primarily active during the night.
node

the point on a cladogram or phyletic chart that shows a line leading to two or more different species "branches" or separates from the main line; defined by synapomorphies.

nomad
an organism that continuously moves in search of resources for survival, such as food.
non-Darwinian evolution
the idea that some genetic changes occur which are not subject to natural selection but rather are a reflection of random processes (e.g., the founder's effect), and that some evolutionary-genetic change is hidden from the editorial powers of natural selection (e.g., silent and neutral mutations).
nonconformity
a break in the geologic record; a line that separates a layer of sedimentary rock deposited over a layer of igneous or metamorphic rock; typically indicates a long-continued erosion event between sedimentary deposition events.
nutrient foramen
a small hole or opening in a bone through which a blood vessels or nerves pass.
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